Over the past year, Americans' support for legalizing pot has surged 10 percentage points.

That's according to Gallup, which has been asking the question since 1969. That means that 58 percent of Americans — a clear majority for the first time in more than 40 years — support legalizing marijuana and just 39 percent say the opposite.

To see the dramatic shift in public opinion, just look at this historical graph from Gallup:

This is also a trend we've seen in other polls. We noted the Gallup poll in 2011 that found support for legalization had reached 50 percent for the first time; and we noted a Pew poll in 2013 that found a 52-percent majority supported legalization for the first time.

This poll shows that support for legalization has accelerated. Gallup explains:

"Success at the ballot box in the past year in Colorado and Washington may have increased Americans' tolerance for marijuana legalization. Support for legalization has jumped 10 percentage points since last November and the legal momentum shows no sign of abating. Last week, California's second-highest elected official, Lt. Gov. Gavin Newsom, said that pot should be legal in the Golden State, and advocates of legalization are poised to introduce a statewide referendum in 2014 to legalize the drug.

"The Obama administration has also been flexible on the matter. Despite maintaining the government's firm opposition to legalizing marijuana under federal law, in late August Deputy Attorney General James Cole announced the Justice Department would not challenge the legality of Colorado's and Washington's successful referendums, provided that those states maintain strict rules regarding the drug's sale and distribution.

"The movement to legalize marijuana mirrors the relatively recent success of the movement to legalize gay marriage, which voters have also approved now in 14 states. Public support for gay marriage, which Americans also overwhelmingly opposed in the past, has increased dramatically, reaching majority support in the last two years."